What causes capacitors to 'splode?

[iisjman07]

I realise I see this quite a lot, but I don't really know what causes capacitors to explode or 'bulge'. Anyone care to spread some light on the subject?

 

[fixitdaz]

Think of an electrolytic capacitors as a battery. They are designed to store a charge and release that charge depending on the specific requirements of the circuit. Inside the capacitor there are two metal plates with dielectric material between them, wrapped in paper, filled with acid (electrolyte), and sealed in its housing or 'canister'. What happens is the flawed electrolyte prematurely deteriorates and dries up. When this happens the capacitance value changes, becomes erratic, and can even short completely, which obviously causes the circuit to malfunction. On your motherboard, this results in system instabilities or complete failure of your board.
Link

 

[ATTech]

I realise I see this quite a lot, but I don't really know what causes capacitors to explode or 'bulge'. Anyone care to spread some light on the subject?

Poor electrolyte creates hydrogen gas. The gas needs to escape, so the top acts as a "pressure release valve" when there is too much build up. This causes the "bulge" when properly released, and an explosion when not. There is a lot of chemistry behind it that I don't understand, but from what I do understand, that's the gist of it.

 

[arrow_runner]

Hooking up a 5v capacitor backwards to 12vdc makes them 'splode. (This is why I shouldn't be left alone with nothing to work on)

 

[fixitdaz]

Hooking up a 5v capacitor backwards to 12vdc makes them 'splode. (This is why I shouldn't be left alone with nothing to work on)

Bigger the cap bigger the bang lol

 

[Styxbound]

Small-time bang. Hook one up to 110volt_but be well away when you connect!

 

[joydivision]

I shorted a massive one once to see what would happen. I had hearing loss for about week afterwards.

 

[Onouris]

I shorted a massive one once to see what would happen. I had hearing loss for about week afterwards.

I stick with disposable cameras, good bang... not quite as dangerous.

 

[joydivision]

I stick with disposable cameras, good bang... not quite as dangerous.

Funilly enough it was a camera flash unit I was taking apart when I shorted the capacitor.

 

[atlanticjim]

I realise I see this quite a lot, but I don't really know what causes capacitors to explode or 'bulge'. Anyone care to spread some light on the subject?

Direct answer (non-technical)

Non-existant quality control in Southeast Asian manufacturers who have flooded the market with crappy caps. Unfortunately the degree of the problem was not discovered until they had been installed on innumberable mobos and other pcbs.

Just another market force that keeps me in business.

 

[Bryce W]

Poor electrolyte creates hydrogen gas. The gas needs to escape, so the top acts as a "pressure release valve" when there is too much build up. This causes the "bulge" when properly released, and an explosion when not. There is a lot of chemistry behind it that I don't understand, but from what I do understand, that's the gist of it.

This is worth a read, especially the part "Cause of the failing capacitors"

http://en.wikipedia.org/wiki/Capacitor_plague

 

[iisjman07]

Thanks everyone; it's true in this business you learn something new everyday

 

[Kitten Kong]

I had one explode on me the other month. Boy was it loud, and whats worse, is I was leant over the pc at the time! Damn thing hit me square in the head!! Only a couple of inches away from my eye. Left a ruddy great bruise, that I can tell you..

I had no indication of it going, just BANG!, and then !%$t!, that hurt; client was stood next to me when it happened, as I was giving the board the once over, checking for bad caps etc.

Almost as bad as the time I had carpal tunnel syndrome in my hands, had the op on my left hand, cleared it fine, then a few months later had the op on my right hand. All was well, then a few days later, poked my hand inside a case, to plug in a psu (I have to admit, i didnt wear a antistatic strap, thought no need, as I stood on concrete all day, wouldnt build up a charge etc, and always touched the case first, before I put my hand in). Then an almighty crackle, fizz, and I blew the board!.

Again client was with me at the time, I supplied and fitted a new board at no cost to my client, as it wasnt their fault it went.

Worst part of this, is it didnt matter what I touched, from bare skin, to wood, to metal, I was getting static shocks. Conductive or non conductive materials, wouldnt make a blind bit of difference. It would only happen with my right hand too.

Went back to the hospital where I had the op done, consultant saw me within hours of ringing them up about the problem. Turned out, I was low on vitamin B1, needed a boost of this.

One in a million chance it could of happened.. Moral of these stories, wear protective glasses, when messing with motherboards, and wear a anti static strap.

 

[KompuKare]

This is worth a read, especially the part "Cause of the failing capacitors"

http://en.wikipedia.org/wiki/Capacitor_plague

Yes, that must be one of the most expensive acts of industrial espionage ever. Ended up costing Dell over $300 million and they were not the only ones affected. Optiplex GX270 had up to 90% failure rates.

I bet that Dell would rather have paid a bit more for some Japanese capacitor rather than Taiwanese ones made with a mis-formulated stolen recipe.

Here's a few more articles:
http://www.guardian.co.uk/technology/blog/2010/jun/29/dell-problems-capacitors
http://www.nytimes.com/2010/06/29/technology/29dell.html
and there tons more. Strangely enough, the Nvdia faulty chips story doesn't seem to have made it to any non-computer newspapers yet.